1. Field of the Invention
The present invention relates to a plasma chemical vapor deposition device that deposits a film on a workpiece by inputting a microwave into the workpiece.
2. Description of Related Art
Research bulletin of the Hiroshima Institute of Technology, Vol. 29 (1995) pp. 29 to 33 discloses one example of a plasma chemical vapor deposition device (hereinafter also referred to as a “PCVD device”) that deposits a film on a workpiece by inputting RF into the workpiece in a state where the RF is offset by a direct voltage. The RF is a wave having a wavelength of around 13.56 MHz. Note that the “RF” is an abbreviation of “Radio Frequency.”
The PCVD device includes a conductor that makes contact with the workpiece inside a chamber, an RF output device that outputs RF, and a direct-current power supply. The RF output device and the direct-current power supply are both connected to the conductor outside the chamber. Hereby, the RF thus offset by the direct voltage can be directly input into the workpiece via the conductor. When the RF is input into the workpiece, a process gas supplied into the chamber is turned into plasma and decomposed around the workpiece, so that a film is deposited on a surface of the workpiece.
Further, in the PCVD device, when a connecting portion of the conductor with the RF output device is assumed a first connecting portion and a connecting portion of the conductor with the direct-current power supply is assumed a second connecting portion, the first connecting portion is placed closer to the workpiece than the second connecting portion. In this case, the RF flows through the conductor not only from the first connecting portion toward a workpiece side but also from the first connecting portion toward a second-connecting-portion side. Accordingly, a lowpass filter is provided in the conductor between the first connecting portion and the second connecting portion. The lowpass filter restrains leakage of the RF toward a direct-current-power-supply side. Note that such a lowpass filter for the RF can be constituted by a lumped constant circuit including electronic components such as a resistor and a capacitor.
In the meantime, as described in Japanese Patent Application Publication No. 2004-47207 A (JP 2004-427207 A), for example, the following method is well known: a microwave having a frequency higher than the RF is input into a workpiece so as to deposit a film on the workpiece. In a case where the microwave is directly input into the workpiece while a direct voltage is applied to the workpiece through a conductor, the RF output device in the PCVD device is replaced with a microwave output device for outputting a microwave. Further, another tubular conductor placed coaxially with the conductor is provided so as to restrain the microwave flowing through a surface of the conductor toward the workpiece from leaking outside halfway. Consequently, the microwave can be directly input into the workpiece, a potential of which is changed by application of the direct voltage.